Exemplary embodiments of the present invention relate to a device for displaying terrain on a display device of an aircraft.
In the context of so-called pilot assistance systems, display instruments for a synthetic external view are always used when outside weather conditions, darkness or so-called brownout/whiteout phases (sand or snow blown up) impair or even completely obscure the pilot's vision. Conventional methods for the generation of a synthetic external view are so-called synthetic vision systems (SVS) or enhanced vision systems (EVS). While in the case of SVS the data to be represented are taken from a database, i.e., terrain and information about obstacles must already be available, in the case of EVS systems cameras or sensors are used in order to directly process the data acquired during the flight.
The prior art is essentially restricted to synthetic vision systems and enhanced vision systems, in which the sensor image is usually represented directly, i.e., two-dimensionally.
WO 2008/018906 describes the data validation of terrain database data by means of sensor data. The method described is based on a fixed number of data points (given by the database) and applies the validation using the acquired sensor data. A point is in this case characterized as “validated, not validated or warning area” as an output.
U.S. Pat. No. 7,148,861 B2 describes data fusion of two data sources at the 2D pixel level. Besides the coordinate systems of the two data sources, a further third coordinate system is introduced that is intended to overcome the different perspectives of the data sources.
EP 1 084 380 B1 describes methods for the visualization of database and sensor data. Further disclosures regarding sensor data fusion can be found in US 2010/0026525 A1 and US patent 2007/0297696 A1.
US 2009/0040070 A1 describes a device for displaying terrain on a display device of an aircraft.
Exemplary embodiments of the present invention provide an improved device for displaying terrain on a display device of an aircraft.
The device according to the invention comprises a synthetic vision system having a terrain and obstacle database, an enhanced vision system having sensors for acquiring terrain data, a height and position sensor for determining flight status data, a display device, a processor for fusion of the data from the synthetic vision system and from the enhanced vision system, the height information generated by the synthetic vision system and the enhanced vision system being stored as pixels in a two-dimensional grid network, a graphics processor that sends the terrain data generated by means of the fusion processor to the display device while taking into account the flight status data determined by means of the height and position sensor.
According to the invention, the fusion processor uses an error function when inserting a pixel into the two-dimensional grid network, the error function providing an estimate of the size of the respective cell, in which the pixel is stored, from the distance of the pixel from the sensor position. In addition to the measured distance between the pixel and the sensor position, other known sensor- or navigation-specific parameters may also be taken into account.
Advantageously, the two-dimensional grid network represents a parameterization of the tangential surface of the terrestrial sphere with a hierarchical non-regular structure and a predeterminable maximum number of cells, the center of the grid network imaging the position of the sensor of the enhanced vision system. The number of cells is not constant, since it depends on the refinement of the cell structure. For the case of the maximum refinement level of a cell, the maximum resolution resulting therefrom may be calculated.
The processor for fusion of the data from the synthetic vision system and from the enhanced vision system will also be referred to below as a ground pixel container.
The present invention involves the combination of the two systems, a so-called enhanced synthetic vision system (ESVS), i.e., the fusion of available terrain and obstacle information that are stored in databases, and 3D sensor data (for example LADAR, RADAR) that are already available in a classified form owing to prior segmentation.
The present invention combines the advantages of synthetic vision systems and enhanced vision systems by real-time segmentation of 3D terrain data acquired by a sensor and fusion thereof with existing terrain and obstacle data from a database. The segmentation of the sensor data in this case decides on a pixel basis whether the respective pixel is to be classified as part of the terrain or as an obstacle. The segmentation is carried out according to methods known from the prior art.
While the pixels classified as obstacles are treated as a 3D point cloud, the so-called “ground pixels” are stored in the ground pixel container. This ground pixel container represents an adaptive grid (i.e., corresponding to the accuracy of a measurement point) that corresponds via its cells to direct sampling of the Earth's surface. Each cell respectively receives a data value, which is then to be considered as a height value for the complete spatial extent of the cell. The ground pixel container in this case supports the “See & Remember” concept, i.e., every spatial region that has been sampled once is stored first in the ground pixel container and subsequently in a database.